Electrical control rheostat



June 13, 1961 P. H. vooRLAs 2,988,720

ELECTRICAL CONTROL RHEOSTAT Filed Aug. 12, 1957 United States Patent O 2,988,720 ELECTRICAL CONTROL RHEOSTAT Peter H. Voorlas, Racine, Wis. Filed Aug. 12, 1957, Ser. No. 677,500 4 Claims. (Cl. 3'38-108) This invention relates to a foot operated electrical control.

Most electrical controls which are presently in use are of the treadle type requiring that the actuating pressure therefor be applied at a particular location on an actuating: lever or treadle member.

Itis an object of my present invention to provide a control which is responsive to actuating pressure applied at any point around the complete circumference of the actuating coverV member.

More specifically it is an object to provide a floating dome shaped, generally circular actuating member responsive to downwardly directed pressure applied at any point on the upper area thereof and provided with an actuating linkage engaged by said dome to vary the current ilow tothe electrical device to be controlled.

Still more specifically it is an object to provide an electrical control mechanism which in the disclosed form constitutes a rheostat unit having a novel and relatively ingenious actuating mechanism including a floating type actuating dome which is responsive Afor actuation to downwardly directed pressure applied to any point on the outer surface thereof.

These and other objects and advantages of my invention will more fully appear from the following description made in connection with the accompanying drawings wherein like reference characters refer to the same or similar parts throughout the several views, and in which:

FIG. l is a top plan View showing my new invention with a portion of the cover dome broken away;

FIG. 2 is a vertical sectional View taken substantially along the line 2-2 of FIG. l;

FIG. 3 is an enlarged lfragmentary bottom elevational view of a portion of the actuating linkage taken substantially along the line 3-3 of FIG. 2; and

FIG. 4 is a fragmentary vertical sectional view taken substantially along the eline 4 4 of FIG. 1.

As illustrated in the accompanying drawing, I provide a suitable base or lower housing element 7 having the feet 8. An intermediate housing portion is dened by a generally cylindrical segment 9 having i-ts lower portion fixed to an upstanding peripheral ange 7a of the base 7. The upper peripheral edge portion of the cylindrical segment 9 is deformed inwardly to provide a retaining lip or flange 9a for interftting with an outwardly deformed lip or ange 10a of a dome shaped member 10 which is mounted for downward shifting movement with respect to the cylindrical segment 9, and is adapted to have any portion thereof depressed downwardly within said segment' 9 for actuating the rheostat mechanism to be hereinafter described.

A mounting plate 1-1 is fixed to the upstanding ilange portion 7a atits ends as by being welded thereto and is arched upwardly to provide clearance for a rheostat body 12 which is connected thereto as by the bolts 12a which suspend said body from an intermediate portion of said mounting plate 11. The mounting plate 11 extends diametrically across the base 7 as best shown in FIGS. l and 2.

The body 12 is formed from any suitable nonconductive material such as the ceramic material illustrated and has a plurality of longitudinally` disposed passages, extending forwardly from the rear end portion thereof. In the forms shown the outermost two passages are provided with suitable conductor and contact elements 12b against which a stack of conductive discs such as the car- Patented June 13, 1961 bon discs 14 are normally engaged with varying degrees of pressure. Each stack of carbon discs 14 has a pressure applying contact member 14a at the end thereof remote from the contact 12b, and made from any suitable conductive material such as carbon. The inner ends of the pressure applying members 14a are enlarged to provide a retaining and abutment flange 14h against which a retainer 14e is engaged. A pair of anchoring bolts 14d extend longitudinally through the ceramic body 12 and threadably engaged with the respective retainers 14C as best shown in FIG. 1. A central recess or passage has a diminished opening at the forward end thereof through which. a plunger rod 13 is slideably mounted and has a rear portion which is enlarged to accommodate a return spring 13a which surrounds the plunger rod 13 which rod extends rearwardly, outwardly beyond the end of said body. A contact crossbar 13b is carried by the rear portion of said plunger rod 13, and a pressure applying spring 13e interposed between a head 13d of said crossbar 13b resiliently holds said cross bar in engagement with return spring 13a. When the rod 13 is projected forwardly to compress spring 13a the crossbar engages the rear ends of the pressure applying contact members 14a and as the spring 13C is then compressed the pressure will be progressively increased on said members 14a to compress the stacks of discs 14 more tightly together and reduce the electrical resistance through each stack of disks.

In' form shown, a grooved actuating bar or member 15 is connected to the forward end of plunger rod 13 as by being threadably attached thereto and said cross bar 15 is engaged by a bell crank actuator 16 having a bifurcated engagement portion 16a which is received in the grooves of cross bar 15 and is disposed therebehind to project said rod 13 forwardly when the upper arm of the the bell crank 16 is depressed on its pivotal mounting pin 18 which is carried by the opposed spaced apart ears 17 fixed to the top of the mounting plate 11. A dome engaging rounded portion 19 is provided on the upper rear end 0f the bell crank 16 and slideably engages the central inside portion of the dome member 10. A return spring 20 normally urges said bell crank back into normal position.

It is apparent that downward shifting movement of the dome 10 will depress the upper end 19 of the bell crank 16 and will project the plunger rod 13 forwardly. The plunger rod, of course, carries the contact crossbar 13b which engages the pressure applying contact members 14a of the stacks of discs to thus reduce the electrical resistance through said carbon discs as previously stated'. The spring 13e compresses during projection of the plunger rod 13 forwardly to produce a yieldable, progressively increasing pressure on said discs. The return spring 13a causes this pressure to be released upon reelase of the upper dome shaped member 10 and works in combination with the return spring 20 to normally hold said dome in upwardly projected position.

A source ofk electricity is connected to the rheostat by connector prongs 21 and 22 and the current passes inwardly through one of said prongs, to one of the terminals 23 or 24 respectively connected thereto by connection wires 25 and to the respectively adjacent stack of discs 14 through the adjacent contact 12b. The crossbar 13b when engaged with the pressure applying members 14a interconnects the rear ends of the stacks of discs 14 and the current flows back through the other stack of discs, the contact 12b and back through the other connector prong in the usual manner. The contact terminals 23 and 24 have a pair of inwardly extending bypass contacts 27 which are adapted to be interconnected directly by a contact bar 26 carried by the rod 13 as best shown in FIG. 3. This contact is made at the extreme end of the stroke of the plunger rod in a forward direction and obviously interconnects the two terminals 23 and 24 directly Without causing the current to pass through the two stacks of carbon discs 14 to thus eliminate from the circuit the electrical resistance of said discs.

The operation of the nheostat disclosed is, of course, to progressively reduce the resistance by compressing the stacks of carbon discs 114 together and eventually bypassing said discs entirely by establishing direct contact between terminals 23 and 24 as stated above.

'It will be apparent that downwardly exerted pressure on any portion of the cover dome anywhere around the periphery thereof or at any other point on the outer surface thereof, will produce actuation of the bell crank 16 and cause the same to compact the carbon discs 14 to reduce lthe electrical resistance through the rheostat. This, of course, produces a relatively simple and easily actuated mechanism which is particularly adapted for use with sewing machine controls and the like. There is, of course, suicient clearance between the lower outer peripheral edge of the cover vdome 10 and the inside wall of the cylindrical segment 9 to permit free and easy shifting movement of the dome 10 or any depressed portion thereof to travel upwardly and downwardly without obstruction. As an outer portion of the dome is depressed the dametrically opposed lip or ange portion 10a thereof will act as a fulcrum to cause the central portion of the dome to be depressed and the bell crank to be thus actuated.

It will be seen that as provided a relatively simple yet highly efficient and easily actuated rheostat which can be operated by downward pressure on any portion of the surface of a generally circular cover dome 10 rather than requiring said pressure to be exerted at a specified location as in most treadle type rheostat mechanisms commonly used for sewing machine motor speed controls.

It will, of course, be understood that various changes may be made in the form, details, arrangement and proportions of the parts shown and described in the specication, without departing from the scope of my invention which generally stated is set forth in the appended claims.

What I claim is:

i 1. A foot operated electric control comprising a base, a generally dome shaped and pivotable actuator element having depending peripheral portion, cooperating stop means on the peripheral portions of the actuator element and on the base and limiting upward* displacement of the periphery of the actuator element, spring means urging said actuator element in an upward direction from the base and cooperating with said stop means for permitting downward tilting of said actuator element and corresponding downward displacement of one side of the actuator element at any point along the periphery of the latter, an electrical control mechanism enclosing movable means to vary the current flow therefrom and mounted on said base, and an actuating lever underlying said actuator element and engaging the same to be operated thereby, said actuating lever being connected with said movable means for varying the current ow through the mechanism.

2. The invention set forth in claim 1 wherein said actuator element is substantially symmetrically shaped, and said actuating lever engaging the actuator element substantially at the center thereof.

3. A foot operated electric control comprising a supporting structure, a generally dome and shell shaped actuator member above the supporting structure, a linkage including a first link centrally engaging the underside of said actuator member and being vertically movable, and said linkage also including a shiftable operating member moved in response to movement of said link, means mounting said linkage on the supporting structure and including resiliently yieldable means charging said link upwardly to normally urge said actuator member upwardly, an electrical rheostat including movable means connected with said operating member and also including a plurality of carbon discs arranged in a stack to be compressed by said operating means to change the electrical conductivity of the stack, and cooperating stop means on the actuator member periphery and on the supporting structure to limit upward movement of one side of the actuator member and to permit downward movement of the opposite side of the actuator member with respect to one side thereof in response to pressure at any point along the periphery thereof so as to tilt the actuator when said pressure is applied adjacent the periphery thereof on said opposite side.

4. A foot operated electrical control comprising a base, a generally dome-shaped and pivotal actuator element having depending peripheral portions, cooperating stop means on the peripheral portions of the actuator element and on the base and limiting upward displacement of the periphery of the actuator element, spring means urging said actuator in an upward direction from the base and permitting downward tilting of said actuator element and corresponding downward displacement of one side at any selected point on the periphery of they actuator element with respect to the opposite side, an electrical control mechanism enclosing movable means to vary the current ow therefrom and mounted on said base and an actuating lever underlying said actuator ele-Y ment and having one end thereof engaging the actuator element to be operated thereby, said actuating lever having its other end connected with said movable means for varying the current flow through the mechanism.

References Cited in the tile of this patent UNITED STATES PATENTS 1,514,546 Lee Nov. 4, 1924 1,550,909 McDougall Aug. 25, 1925 1,614,887 Hill Jan. 18, 1927 1,777,988 Wilms Oct. 7, 1930 1,988,796 Hueber et al. Ian. 22, 1935 2,117,257 Schenk May 10, 1938 2,333,814 Perkins Nov. 9, 1943 2,424,529 Wimmer July 22, 1947 2,472,604 McDonald June 7, 1949 2,536,012 Turner Dec. 26, 1950 

